In measles, herpes, visna and vesicular stomatitis virus infections, viral induced membrane changes as well as the modification of the infected cell surface in the presence of antibody have been explored with high resolution scanning EM, freeze-fracture and immunolabeling techniques using Protein A-Peroxidase. Some strains of measles and vesicular stomatitis virus replicate mostly in neurons and viral antigens are distributed at various sites on the cell body and the neuritis. In the MS plaque important differences are seen between axonal membranes and astrocytes. BIBLIOGRAPHIC REFERENCES: Dubois-Dalcq, M.: Slow Virus Infection of the Central Nervous System Investigational Approaches to Etiology and Pathogenesis of these Diseases. Comment Ter Meuler, V. and Katz, M. Springer-Verlag chapter 3, p.68-70, 1977. Chapter 8, p. 127-128, 1977. Dubois-Dalcq, M., Rodriguez, M., Reese, T. S., Gibbs, C. J. and Gajdusek, D. C.: Search for a Structural Marker inside the Neural Membrane of Scrapie Mice (a freeze-fracture study). Laboratory Investigation 36: 547-563, 1977.